Cavitation refers to the process of forming partial vacuums within an unfilled space in a liquid. This can be done in a number of manners, such as through the use of a swiftly moving solid body (as an impeller), hydrodynamically, or by high-frequency sound waves.
Apparatuses and methods for producing cavitation are described in U.S. Pat. Nos. 3,399,031; 4,675,194; 5,026,167; and 5,837,272. One particular apparatus for producing hydrodynamic cavitation is known as a SONOLATOR® high pressure homogenizer, which is manufactured by Sonic Corp. of Stratford, Conn., U.S.A. The SONOLATOR® high pressure homogenizer directs liquid under pressure through an orifice into a chamber having a knife-like blade therein. The liquid is directed at the blade, and the action of the liquid on the blade causes the blade to vibrate at sonic or ultrasonic frequencies. This produces hydrodynamic cavitation in the liquid in the area around the blade.
The SONOLATOR® high pressure homogenizer has been in use for many years, and has been used as an in-line system, single or multi-feed, to instantly create fine, uniform and stable emulsions, dispersions, and blends in the chemical, personal care, pharmaceutical and food and beverage industries.
It has been found, however, that while such a high pressure homogenizer works well at certain pressures, the use of such an apparatus is limited above certain pressures (e.g., greater than or equal to about 1,000 psi (about 7×106 Pascals)), particularly when run continuously at such pressure. The limited use is due to high blade wear and corrosion. Blade wear can even occur at a pressure lower than 1,000 psi. (for example, at a pressure greater than or equal to about 500 psi. (about 3.4×106 Pascals)) over shorter time periods if the liquid contains solids, particularly solid crystals. In addition to blade wear, the pressurized fluid may cause both erosion and corrosion to take place at the orifice, thus, further deteriorating the overall performance of the apparatus.
The search for improved apparatuses and methods for mixing by producing shear and/or cavitation, and components for such apparatuses has, therefore, continued. In particular, it is desirable for apparatuses and methods for mixing by producing shear and/or cavitation to be developed that overcome the aforementioned problems. The search has led to the development of vibratable blades for those apparatuses that utilize blades, which have improved vibration characteristics.